A. The Prior Art
West German Pat. DT-AS 2 159 522 has a cylindrical body provided along its front end with a writing tube wherein the falling weight with the cleaning wire is passed through an internal boring. In addition, this cylindrical body has a groove facing outward, which can be inserted into a cartridge element which has along its inner surface an ink compensating chamber. The aligning surfaces between the cartridge element and the cylindrical shell are slightly conical relative to each other, so that the cartridge element can be released from the mounting walls after a brief axial movement in respect to the cylindrical shell. In this fashion it can be pulled from the cylindrical shell without further difficulties.
Since, as a result of dried ink, it can happen that the shell element becomes glued along the frontally opened slot of the cylindrical shell and then cannot be released by simple pulling, this already known capillary tube pen point is provided with a thread consisting of a number of protruding thread courses in the front part of the cartridge element as well as correspondingly recessed threads in the frontal part of the cylinder shell. This allows for only a limited insertion of the cartridge element up to a given depth into the annular tee-slot which faces forward. In order to have acomplete and satisfactory insertion, a screwlike motion is required. By utilizing such a thread arrangement and as a result of the required screw-like turn, it is possible to achieve -- by properly turning the cartridge element -- a force, acting in the axial direction that will affect a separation of aligning surfaces of cylinder shell and cartridge element. However, this thread arrangement makes more difficult the insertion of the cartridge element into the cylinder shell. Furthermore, this type of construction requires special dies when using the injection mold process and this causes an increase in the production costs.